1. Field of the Invention
The present invention relates to a diode having a structure with whose dynamic resistance lowered.
2. Description of the Related Art
A diode which has a pn junction has been known. Electric current, which flows when the forward voltage is applied to the diode, increases rapidly at the point where the forward voltage exceeds the potential difference between the conduction bands of p and n layers. The larger gradient of the characteristic curve between electric current and voltage in the dynamic range is, the more suitable the diode becomes to use as various devices.
However, a problem persists in the gradient. The gradient of electric current and voltage characteristics could not be varied because it is determined by materials which form the diode. Therefore, further improvement has been required, as presently appreciated by the present inventors.
As a countermeasure, reflecting carriers by forming cladding layers with multi-quantum well structure of a series of a pair of a first and a second layers has been suggested by Takagi et al. (Japanese Journal of Applied Physics. Vol. 29, No. 11, November 1990, pp. L1977-L1980). This reference, however, does not teach or suggest the values of the kinetic energy of carriers to be considered and the degree of reflectivity of carriers is inadequate.